Improving a mother-to-be’s ratio of omega-3s to omega-6s may boost birth weight of the infant and increase the duration of pregnancy, says a new study.

Data from 6,974 pregnant women and their infants participating in the Generation R Study indicated that a higher maternal omega-3 to omega-6 ratio in mid-pregnancy was associated with a faster growth of the fetus, including weight, length and the head.

“In this large population-based prospective study, we found that a higher maternal n-3:n-6 PUFA ratio was associated with a better fetal health, determined by a higher fetal growth velocity already from mid-pregnancy onward, a higher birth weight and a longer duration of pregnancy,” ​wrote the researchers in Clinical Nutrition​.​

“These findings seem to be partly accounted for by higher percentage of maternal mid-pregnancy n-3 PUFA in [glycerophospholipids – the major constituents of cell membranes].”​

Health benefits and healthcare cost savings ​

The study adds to a growing body of science supporting the benefits of omega-3 supplementation on pregnancy and the health and development of the infants.

Data from the Kansas University DHA Outcomes Study (KUDOS)​ indicated that universal supplementation with DHA (600 mg per day) during the last two trimesters of pregnancy led to significant reductions in early preterm birth. This would result in cost savings of $1,678 per infant. Taking out the $166.48 cost of the DHA supplements for 26 weeks and a $26 increase in maternal care costs, the net saving became $1,484.

Study details​

The Generation R Study Group scientists analyzed data from almost 7,000 pregnant women and their infants and found that a higher omega-3 to omega-6 ratio in the mother mid-pregnancy was associated with statistically significant improvements in growth velocity of the weight of the fetus, as well as in the length and head size.

In addition, a higher ratio of omega-3 to omega-6 was associated with a higher birth weight, and a longer pregnancy.

Consistent associations were also observed for omega-3:omega-6 ratio and the weight of the placenta.

“The close correlation between placental and birth weight illustrates the main importance of placental function for the growth and development of the fetus,” ​wrote the researchers. “As the placenta is an organ of extra-embryonic origin, the observed associations with placental weight might also reflect effects early in pregnancy. ​

“We describe the patterns of the relationship of n-3 and n-6 PUFAs with placental weight similar to our findings with birth weight. Apart from maternal dietary intake, the fetal supply of fatty acids also depends on the fatty acid release from the maternal adipose tissue and the placental transport.”​

Effects on inflammation​

Commenting on the potential mechanism(s) of action, the researchers noted that, while these are not fully elucidated, there is evidence to support the effects of omega-3s and omega-6s in fetal growth, “including energy storage, oxygen transport and cell membrane functioning”​, they said. “Furthermore, these PUFAs have roles in inflammation and are suggested to act as important mediators of gene expression”​

“Future research should address underlying pathophysiological mechanisms and the long-term effects on infant health,” ​they concluded.